num-islands-whiteboard-exercise

// - 2D grid map of 1's & 0's - 1 = land, 0 = water (strings)
// - count number of islands
// All 4 edges of the grid are considered water

/*
Input: grid = [
  ["1","1","1","1","0"],
  ["1","1","0","1","0"],
  ["1","1","0","0","0"],
  ["0","0","0","0","0"]
]

// 2 islands
[
  ["1","0","1","1","0"],
  ["1","1","0","1","0"],
  ["1","1","0","0","0"],
  ["0","0","0","0","0"]
]

// 2 islands
[
  ["1","1","0","1","0"],
  ["1","1","0","1","0"],
  ["1","1","0","0","0"],
  ["0","0","0","0","0"]
]

Output: 1
*/

/*
Output: number of islands in grid (integer, >= 0)
Input: matrix of 0's & 1's (strings) representing a block of land & water
Constraints: n by m grid, no irregular grids, O(?) time, O(?) space
Edge cases: [] => 0, [[]] => 0, 
*/

// Island:
// - surrounded on all sides by water (0)
// - surrounded on n sides by 0's, and on 4-n sides by an edge

// Pseudocode:

// Keep a record of which cells in the grid have been visited already
// Track the count of islands thus far, 0 initially

// For each row of cells in grid
  // If first row, record positions of land cells
  // Else not first row: 
    // For each cell in row
      // Compare the position of the current cell, if it's land, to recorded positions
        // As long the current cell is a land cell, keep the recorded position as is
        // Else check the previous row's record for continuous land: (example at position 2, need to check if 1, 2, 3 all exist as records in recorded positions) (position - 1, position, position + 1 all exist in recorded positions)
          // If exists, remove the current position from recorded positions (prepare for next row)
          // Else 
  

// 0, 1, 2, 3
// 



// Return the count